Problem: Constraints

* H is an integer between 2 and 50 (inclusive).
* W is an integer between 2 and 50 (inclusive).
* s_{i, j} is `.` or `#` (1 \leq i \leq H, 1 \leq j \leq W).
* s_{1, 1} and s_{H, W} are `.`.

Input

Input is given from Standard Input in the following format:


H W
s_{1, 1}s_{1, 2}s_{1, 3} ... s_{1, W}
s_{2, 1}s_{2, 2}s_{2, 3} ... s_{2, W}
:   :
s_{H, 1}s_{H, 2}s_{H, 3} ... s_{H, W}


Output

Print the maximum possible score that Snuke can achieve, or print -1 if the game cannot be completed.

Examples

Input

3 3
..#
#..
...


Output

2


Input

3 3
..#
..
...


Output

2


Input

10 37
.....................................
...#...####...####..###...###...###..
..#.#..#...#.##....#...#.#...#.#...#.
..#.#..#...#.#.....#...#.#...#.#...#.
.#...#.#..##.#.....#...#.#.###.#.###.
.#####.####..#.....#...#..##....##...
.#...#.#...#.#.....#...#.#...#.#...#.
.#...#.#...#.##....#...#.#...#.#...#.
.#...#.####...####..###...###...###..
.....................................


Output

209

Solution (in PYTHON3):

Solution:
from collections import deque

H, W = map(int, input().split())
S = [input() for _ in range(H)]

T = [[None] * W for _ in range(H)]
T[0][0] = 1
D = deque([(0, 0)])
while D:
    h, w = D.popleft()
    for dh, dw in ((1, 0), (0, 1), (-1, 0), (0, -1)):
        if 0 <= h + dh < H and 0 <= w + dw < W and S[h + dh][w + dw] == '.' and T[h + dh][w + dw] is None:
            T[h + dh][w + dw] = T[h][w] + 1
            D.append((h + dh, w + dw))

if T[H - 1][W - 1] is None:
    print(-1)
else:
    print(sum(s.count('.') for s in S) - T[H - 1][W - 1])